/*
type int
parse 5 5
parse 2+3 5
parse '2*3' 6
parse '2+3*4' 14
parse '2+3*4+5*6' 44
noparse '' Sum 1
noparse 4+ Sum 3
*/

Sum <- p:Product "+" s:Sum -> { p + s }
    / Product
Product <- d:Decimal "*" p:Product -> { d * p }
    / Decimal
Decimal <- [0-9]+ -> { atoi(ref_str()) }
